PROJECT SUMMARY Head and neck squamous cell carcinoma (HNSCC) remains a challenging clinical problem because of the persisting high rate of local and distant failure. Targeting epidermal growth factor receptor (EGFR) is a rational strategy given that more than 90% of HNSCC overexpress EGFR which is associated with poor prognosis. However, the clinical benefit is dampened significantly in HNSCC patients as EGFR-targeted therapy cannot suppress EGFR-independent mitochondrial oncogenic signaling, which emphasizes the need for further insights into novel comprehensive and efficacious treatment of HNSCC. We now have data demonstrating that the ATPase family AAA-domain containing protein 3A (ATAD3A), a mitochondria-localized enzyme, is required and sufficient to favor head and neck tumor growth and progression by upregulating EGFR-independent mitochondrial oncogenic signaling. These novel observations and findings raise the possibility to develop novel combination regimens by co-targeting ATAD3A and EGFR in order to eventually increase cure rate in HNSCC. The central hypothesis of this proposal is that ATAD3A forms oncogenic signaling molecules with PKC? and ERK1/2 at the mitochondria to promote head and neck tumor growth and progression, and dual inhibition of ATAD3A and EGFR represents a promising strategy to enhance anti-HNSCC treatment. The strengths of our studies should interest a range of cancer scientists and clinicians, who seek to understand the biological consequences of cancer treatment and to assess the feasibility of manipulating mitochondrial signaling pathways for therapeutic purposes. The hypothesis will be tested in the following Specific Aims. Aim 1 is to explore functional regulation and role of the mitochondrial PKC?-ATAD3A complex in HNSCC cells. Aim 2 is to illustrate the mechanism underlying ATAD3A-dependent mitochondrial ERK1/2 activation in HNSCC cells. Aim 3 is to develop new therapeutic approaches to control HNSCC progression by co-inhibiting ATAD3A and EGFR. Our overarching goal is to improve EGFR-targeted therapeutic efficacy in HNSCC by simultaneously suppressing ATAD3A-mediated mitochondrial signaling, with tumor-targeting multifunctional nanoparticles for the co-delivery of erlotinib/siRNA (anti-ATAD3A). Results from this project will significantly impact upon the design and execution of novel combination regimens for EGFR-positive HNSCC.